Breakfast and heart disease

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Behind the Headlines

Tuesday October 26 2010

It's important to eat a healthy breakfast whenever possible

“Skipping breakfast too often can put you at risk of heart disease,” the Daily Mail has reported. The newspaper says that this may be because people who skip breakfast are more likely to have poorer diets and take less exercise.

Contrary to the newspaper headline, this study did not look at heart disease. Instead, it looked at the link between skipping breakfast as a child and as an adult, and certain risk factors that may be associated with heart disease, such as waist circumference and levels of cholesterol in the blood.

The study has a number of limitations, including the fact that two thirds of the participants assessed as children were not followed-up as adults. Also, diet was thoroughly assessed only once rather than followed over time. The limitations to this study mean that by itself it cannot prove a link between skipping breakfast and changes in metabolism or cardiovascular risk. However, this does not necessarily mean that this link does not exist. Overall, people should aim to have a healthy, balanced diet, and eating a healthy breakfast is part of this.

Where did the story come from?

The study was carried out by researchers from the University of Tasmania and other research centres in Australia. It was funded by the Australian National Health and Medical Research Council, the Australian National Heart Foundation, the Tasmanian Community Fund, Veolia Environmental Services, Sanitarium, ASICS and Target. The study was published in the peer-reviewedAmerican Journal of Clinical Nutrition.

The Daily Mail has generally reported the study accurately, but its headline suggesting a link with heart disease is not supported by the research.

What kind of research was this?

This was a prospective cohort study, which assessed whether skipping breakfast in childhood and adulthood was associated with markers of cardiovascular and metabolic risk.

This study design is appropriate for looking at the relationship between childhood breakfast habits and cardiometabolic risk. However, the assessments of adult breakfast habits and cardiometabolic risk occurred at the same (a single point in time), meaning that this study cannot say for certain whether adult breakfast habits had influenced the participants’ cardiometabolic risk.

In addition, this study only set out to assess markers of cardiovascular and metabolic risk, but not instances of cardiovascular or metabolic disease themselves. Therefore this study cannot tell us whether people who skipped breakfast as children would be at greater risk of conditions such as heart attacks or diabetes.

What did the research involve?

The researchers assessed breakfast habits in a sample of Australian children aged 9 to 15 years old in 1985. These participants were then followed-up between 2004 and 2006 when they were aged up to 36 years old. They reported their adult breakfast habits, and they also had their waist circumference and their blood levels of sugar (glucose), insulin and fats (lipids) measured. The researchers then looked at whether skipping breakfast in childhood and adulthood were associated with cardiometabolic risk factors, such as larger waist circumference.

The original 6,559 children taking part in the study were selected to be representative of the general population in Australia. They were asked whether they usually ate something before they came to school, and their weight and height were measured.

About a third of the children assessed were followed-up as adults (2,184 people). These participants filled in a more complex food frequency questionnaire about how frequently they ate specific food and drink items over the past year. The questionnaire also recorded their meal patterns over the previous day (what time they ate and drank and how much). Participants who did not eat between 6 and 9am were considered to be skipping breakfast.

Participants also reported on other aspects of their lifestyle (e.g. physical activity), and were given a healthy lifestyle score based on these factors and how healthy their diets were. They also had their blood pressure measured. Some of the participants (1,723 people) had their weight, height and waist circumference measured. In total 1,730 participants also provided blood samples after fasting for 12 hours.

Based on the data collected, the researchers grouped participants into:

those who ate breakfast as children and as adults (1,359 people)

those who skipped breakfast as children only (224 people)

those who skipped breakfast as adults only (515 people)

those who skipped breakfast as children and as adults (86 people)

The researchers then compared the waist circumferences and blood results between these groups to see if there were any differences. In these analyses they took into account age, gender, education, occupation, smoking, TV viewing, socioeconomic status as a child, diet factors and healthy lifestyle score.

What were the basic results?

Most people (62.2%) reported eating breakfast as a child and as an adult. People who skipped breakfast as an adult had less healthy lifestyles than those who did not.

People who skipped breakfast during both childhood and adulthood had larger waist circumferences than those who ate breakfast at both ages. The difference in average waist circumference between these groups was 3.7cm after taking into account other factors that could affect results. People who skipped breakfast as children and as adults also had higher insulin levels in the blood, higher levels of total cholesterol, and higher levels of LDL cholesterol (sometimes called ‘bad’ cholesterol) than people who ate breakfast at both ages.

How did the researchers interpret the results?

The researchers concluded that “skipping breakfast over a long period may have detrimental effects on cardiometabolic health”.

They say that promoting the advantages of eating breakfast could be a simple and important public health message.

Conclusion

This study suggests a link between skipping breakfast and cardiometabolic risk factors, such as larger waist circumference and higher levels of cholesterol. There are a number of points to note when interpreting this study:

A large proportion (about two thirds) of the initial sample of children were not followed up in adulthood. Inclusion of all of the participants may have given different results.

This study did not assess clinical outcomes such as cardiovascular or metabolic disease, therefore it is not possible to say how these outcomes are affected by skipping breakfast. Although factors such as waist circumference or blood cholesterol or insulin level may be related to a person’s risk of cardiovascular or metabolic disease, it is not possible to say whether the differences seen would be great enough to influence risk of developing these conditions.

The number of people who skipped breakfast as a child and as an adult was small - only 86. Therefore, results for this small group may not be reliable.

The study did not look at what people ate for breakfast, as this is also likely to affect their cardiometabolic risk.

Breakfast eating was only assessed at two time points, and may have differed over the years between these time points.

Although the researchers took into account factors that could affect results, these and other factors may still be having an effect. For example, although adult diet (at the time of measurement) was taken into account, diet in childhood, adolescence and earlier adulthood was not.

Overall, this study alone does not conclusively prove a link between skipping breakfast and poorer cardiometabolic risk markers.